The Web Server Gateway Interface (WSGI) is a standard interface between web server software and web applications written in Python. Having a standard interface makes it easy to use an application that supports WSGI with a number of different web servers.

One implementation is wsgiref that was added to Python 2.5 Standard Library.
Here is a simple web application that writes "Hello World":

Simple eh?
This is just a start, now we can add more features, like encapsulate the start_response method and add some kind of HttpResponse.
I don't what do reinvent the wheel here and add another web framework to Python, just like Joe Gregorio says in this article. But to prove how trivial is to make a simple framework with WSGI and don't worry about the deployment at development phase.